Imagine you were a weapons scientist. You're doing some work on a new rpg. Now think about what would happen if you built something, where the charge came out of the barrel and dropped 2ft in front of you. You're not out on the field yourself. But you're in the lab, and yesterday the person who bought those rpg's found out that they're fake news. What do you think will happen to you today? That is what keeps your work honest.
On the other hand, what will happen if Greta finds out that your climate model was fake news?